When it comes to healthy eating, you likely focus on three main macronutrients: carbs, fat and protein. However, another important macronutrient many of us don’t consume enough of is fiber. The average American adult consumes only 17 of the recommended 25–30 grams per day.
The F-Factor Diet, created by registered dietitian Tanya Zuckerbrot, brings fiber to the forefront. Zuckerbrot claims the plan helps you feel fuller, leading to weight loss. Appealing as that may be, there are a few things to consider before you try the F-Factor Diet.
Research links high-fiber diets with benefits such as a decreased risk of heart disease, diabetes and colorectal cancer. Fiber may also promote a healthy gut microbiome and support weight loss. “There’s good evidence that, as part of a healthful eating plan, fiber can help you manage your weight more easily,” says Samantha Cassetty, RD.
While F-Factor protein powder and bars can be found (offering 20 grams of fiber per serving), they’re highly processed and the fiber comes from ingredients such as guar gum, corn fiber and chicory root. Instead, you can save money by opting for whole-food sources of natural fiber, which contain other essential vitamins and minerals. “I generally recommend getting fiber from whole foods like pulses, veggies, fruits and whole grains,” says Cassetty. Think: beans, peas, lentils, produce, quinoa, rice, farro, etc.
The F-Factor Diet recommends eating 35 grams of fiber a day, which is more than the USDA’s current guidelines. Given that many people currently only consume half of that, it’s important to work up to this goal. “I always advise clients to increase their fiber intake slowly,” says Amy Gorin, RD. “If you are not used to consuming large amounts of fiber, increasing intake quickly can cause symptoms such as bloating and gastrointestinal discomfort.” Also, be sure to drink plenty of water to help prevent constipation, she adds.
The F-Factor Diet has three phases, each with a different target number for net carbs (aka the total amount of carbs minus fiber). The first two weeks, you restrict to less than 35 grams of net carbs; the next two weeks allow up to 75 grams of net carbs, and the final phase increases to 125 grams net carbs. During phase one, you also eliminate starches and starchy vegetables, most dairy and medium- to high-fat meats and restrict fruit to one serving. “If you’re currently eating a lot of starchy carbs like pasta (helpful for endurance training), this plan might be harder to follow since it limits those items,” says Cassetty.
The plan gives you advice on how to eat out and order takeout while sticking to the protocol. “But you might need to make a lot of menu modifications, order things like dressing on the side or make a meal out of various sides,” adds Cassetty.
Moderate drinking is allowed on the plan, although lower-calorie options such as vodka soda are encouraged. “It’s not sustainable to overly restrict alcohol, dessert or anything else,” says Cassetty. “I’d suggest thinking about what trade-offs you’re willing to make. For example, if you’re going out to eat, maybe you have a drink but skip the bread basket.”
The F-Factor Diet advertises you can “Work out less!” Zuckerbrot also says to avoid cardio because it “can stimulate appetite.” However, this claim has not been proven and a 2018 review published in Nutrients concluded more research is necessary, as the effects of exercise on hunger appear to vary from person to person. Whether or not you’re exercising for weight loss, regular movement is undeniably important for overall health. Both Gorin and Cassetty recommend finding activities you enjoy (whether that’s going for a walk, strength training or swimming) and want to participate in consistently.
“Even though the diet is somewhat flexible compared to many other diets out there, it still has many restrictions,” notes Gorin. “I would not recommend this diet for someone who has a history of disordered eating.” Cassetty agrees, pointing to the fact that, in addition to rules, you also need to track fiber, which could lead to overanalyzing every morsel that passes your lips.
Fiber may help you feel fuller longer, in turn helping you eat less and possibly lose weight. However, this diet isn’t a guarantee that you will slim down the first month. “Weight loss is an outcome that’s hard to promise or predict,” says Cassetty. “Even when my clients want to lose weight, I generally discourage thinking about a goal weight or a weekly scale goal. Being overly focused on weight loss alone or a goal weight can be self-defeating and stressful. The extra stress makes it harder to lose weight, and when you don’t hit your targets, it generally makes you feel crummy.” She recommends focusing on reaching a healthy, happy place instead, which includes not only eating nourishing foods and staying active but also managing stress well, prioritizing relationships with friends and family and getting quality sleep.
While the “phase” style of the F-Factor Diet may promote fast weight loss, keeping you motivated to carry on, it also could also act as a trap. “When people get motivated by initial weight loss, it can be hard and discouraging if weight loss slows down in the next phase,” explains Cassetty. Additionally, according to the plan, if you want to lose more weight once you reach the third phase, you should go back to the first two more-restrictive phases. “If you are gaining weight [in phase three] and then moving back to another phase to re-lose it, that’s a sign the plan is probably not sustainable. It’s likely phase one is too restrictive for the long-haul,” says Cassetty.
Other than the fact that the F-Factor Diet downplays exercise, Gorin doesn’t see too many negatives with the overall plan. Nor does Cassetty, so long as you focus on wholesome sources of fiber over manufactured ones and keep in mind diet is only one part of losing weight (if that’s your goal). “What you eat is just one piece of the puzzle,” says Cassetty. “Weight loss also involves learning other skills, like coping with stress and other emotions in a healthy way, getting enough sleep and learning to stop eating when you’re somewhat full rather than stuffed.”
It’s also important to note that the F-Factor Diet in particular has not been studied, adds Cassetty. As with any diet, you should always consult your physician or a healthcare professional before trying it.